Although I suggested a rodent habitat for my first orbital life support test unit, I have decided that a mini aquarium would be better. With one liter of water and one small goldfish, this minimizes the system complexity and provides nice internet photos of Wanda swimming in zero g. The system is only mildly simpler since fish also need oxygen, produce CO2 and waste, and need a food supply. Goldfish are robust, and have thrived under my inept care.

The goal, of course, is to produce a test system which would enhance the credibility of the promised systems, yet be so small and light that Bigelow or Elon Musk would fund piggyback orbital tests for the publicity (or even humor) value. I will have no difficulty in demonstrating that a compact system can sustain my life, but neither Bigelow or Musk will be easily persuaded to allow that demonstration to be moved to orbit.

In the “Help Please”, category, I will need a “Fish Stick”. That is, a stick of fish food, not a food stick made of fish. It must be stable, but capable of being pushed or extruded into the aquarium day by day. (Marshmallow? Don’t anglers use it for bait?) If nobody knows of a good answer, invent one. There are a lot of aquarium owners who could use an automatic feeder when they are on vacation.

There is quite a bit more to having a fish survive then just food and water. Fish living in an enclosed environment only manage to do so because of symbiotic bacteria that convert the fish's waste products and excess food into mostly harmless nitrates. With out these bacteria the fish would quickly die in a sea of its own waste.

I would suggest that the environment being used for the experiment be seeded by allowing the fish to live in it normally for at least a month before any additional stresses are applied to the fish (such as zero-g, etc). If the fish can surive the first month in the new environment than it might just live long enough to allow you to gather any useful data during the test.
Good luck,
-Rich

I was planning on using both filters and a small reverse osmosis (RO) concentrator for dissolved wastes including nitrates. This is a version of what I will be using for human wastes, and uses a modification of the normal RO filter process. I plan to adjust solution PH, with continuous sensing, plus monitor PCO2 and PO2. A “dissolved solids” (electrical conductivity) probe will monitor the RO effectiveness. Obviously forced circulation is mandatory, with no bubble systems! (Gas transfer will be through hydrophobic membranes – like Gore Tex Teflon). I plan on using a low level of Ozone, which I understand is common in aquariums, since harmful bacteria are always a problem.

I have been wondering about ORP (Oxidation Reduction Potential) which is used with swimming pools, but that may only be to monitor Chlorine levels. I hope I don’t have to add any more monitors, but am not sure. I think I can get this as a flight weight system under 5 kilograms (including a one liter “fish tank”). That also includes a small digital camera and LED lights.

I agree that lab demonstration of the system is mandatory. Actually, I expect to “use up” Wanda 1, Wanda 2, … during system development. A “zero G” aircraft flight demonstration of the system (with fish) will probably be necessary to develop credibility for orbital testing as well.

Obviously a wide range of fish could be used, but the goldfish I have “owned” were very robust, and tolerant of demanding conditions. (One spent two weeks in the refrigerator, in an experiment, to see if it minded the cold: it seemed quite happy). This is of course intended to demonstrate some hardware for human life support, so it is a bit complex.

If there are other things I need to address, please let me know. Otherwise, I will be asking for help after I “use up” Wanda 1. Considering the small size of my suggested fish tank, she will outgrow it long before I expect to be permitted to send her into orbit!

One of the reasons Goldfish makes a good small tank fish is because when the water gets bad ( for example: before the bacteria colony gets big enough to cleanup the wastes in the water) the goldfish actually breathes by gulping air from just above the waters surface. The Goldfish has a special organ that allows it to breathe air directly. So i am not so sure that a Goldfish will be any better than any other fish such as a tetra when it is in a fully water enclosed envirionment.
However, one thing that i have learned from experience is that fish growth rate and life-span seems to be related to the amount of food available to it. For example: most aquarimun sized fish can get along just fine with no food for 2 weeks at a time with no ill effects at all. While feeding to much will cause a rapid death sequence in the tank. I have kept fish alive and breeding for more than twice thier expected live spans by just feeding sparingly and maintaining good water quality.
-Rich

Thank you again. I didn’t know any of that. I have seen my goldfish sucking a lot of air, but I didn’t know why. The low food tolerance is a surprise, and makes things easier. (Low, not zero: I am not going to build a system which intentionally starves my fish!)

My wife has kept goldfish for the last 5 years. Our largest is nearly 8" long. She would likely concur as to the infrequent, sparing feedings being important for the lifespan of the fish. The size of the fish is more a criteria of the tank their in instead of the food. A well fed fish in a small tank won't get as big as the same fish and feeding schedule in a bigger tank. She's also been trying to tell me all about those waste munching bacteria.

Here's the bigger rub though. Goldfish and Bettas go to the surface for air only when there's not enough oxygen in the water. The way air gets into the water is through surface agitation. The air that's pumped into the water looks cool, but it doesn't get absorbed. Instead, it agitates the surface of the water causing waves. So the aquarium water gets oxygenated the same way that a lake or the ocean does.

In zero-gravity space, the water'd float all over the enclosed aquarium, and the air in the tank'd form perfectly round, bouncy bubbles since there's no gravity to force separation of the water from the air. In order to separate the water from the air, produce a surface to have a wave on, and allow the fish to breathe at all, the entire tank'd need to be put on a centrifuge and spun. It doesn't need to be very fast but enough of a speed to force the water "down" and allow the air to "rise". The only precaution is that water is a bit heavy.

As to feeding, goldfish and other hardy breeds are widely adaptable to their environment and feeding situaiton so long as you make no abrupt or sudden changes. My wife sometimes makes her own fishfood which ends up being a thick, gloppy mixture that she spoons into the water. Some fish prefer it to their usual flake food. A thick gloop would be ideal, however, for an automated feeding system since it could be pushed through the tube that's connected to the tank.

Another option might be to find a vegetable or fruit that the fish would be able to snack on for a short duration trip. In which case, you could simply put the cucumber/zucchini/etc. into the tank at the start and not worry about food for the initial experimental period. Overfeeeding is more common with the concentrated flake food that we usually feed them. Kinda like the difference between eating an apple and drinking a half-gallon of apple juice and getting diarrhea. The fiber in the apple prevents you from getting too much juice whereas a half-gallon of apple juice uses dozens of apples that you'd never be able to eat whole.

The biggest difference between swimming pools and fish tanks is that fish tanks are all about balancing life vs. life while swimming pools are designed to KILL everything that could possibly be alive in the water except the swimmers.

Thanks for the input. Your experience with "paste" fish food is interesting, as this would in fact be a very handy way to feed fist for a long duration. Considering the cost of getting anything into orbit, I am not thinking about short term tests. A more reasonable goal will be to attempt to develop a long duration experiment and see how long the fish can actually be kept alive in "zero g".

Incidentally, what do you know about Chlorella algae as a fish food? For a really long term experiment - and demonstration of possible multidecade human life support - algae aquaculture (using Sunlight as an energy input of course) is very promising and produces both the food, Oxygen and waste removal. (I understand that keeping a closed system like this in "automatic" balance is difficult - nearing impossible. A practical form would monitor the chemical environment and make adjustments as needed. Probably some mineral adjustments would be necessary in any case.)

Back to Oxygenating the water (and removing CO2), neither the surface waves or the bubbler would work in “zero g”. A small centrifugal unit (like what I am now using for “zero g” distillation of water) could be used to Oxygenate flowing water with bubblers, and the flowing water would be returned to the tank just as water Oxygenated at the ocean surface reaches the depths by circulation. On the other hand, I have had reasonable success with Membrane Gas Transfer (usually using Teflon films). This is not the simplest arrangement, but it works well in “zero g” has proven to not only prevent bubble formation, but to be able to absorb bubbles created for other reasons. The circulating water would be pumped through a membrane, gas transfer unit.

Frome the various sources that I've read, Chlorella algae is best found at an herb/health food store (sold dried in capsules as a supplement) instead of in a commercial fish food package. This is promoted as both more cost effective as well as more nutritious. As Chlorella grows, it floats in the water but will attach itself to a substrate and form large chains of algae that are a form of "slime". Another common aquarium algae is Spirulina.
<http://www.azdr.com/Tadpoles.html>

Some commercial fisheries, in order to increase the Chlorella growth, use scube type equipment to artificially increase the CO2 level of the water.
<http://www.wattleydiscus.com/Products.htm>

Additional information about Chlorella production was found on this producer's website. As much marketing hype as factual information, it's still educational.
<http://www.wilson-groups.com/main_products.htm>

According to Kevin Keely and his book "Out of Control" (available to read online), the astronauts endure very poor atmospheric conditions. Some early Russian experiments with Chlorella produced very unpredictable results and a wildly uncontrollable atmosphere. Bios3 was their most successful effort, but still nowhere near what would be considered quality air. Increasing the complexity of the process (Biosphere2) made better air, but it also made it more impractical for space exploration.
<http://www.kk.org/outofcontrol/ch8-c.html>

The Interstellar Society has a good writeup on this as well at their website. According to the Russians, Chlorella is inedible to humans. Therefore, an intermediate is necessary to eliminate overproduction of Chlorella and provide a product for human consumption.
<http://www.interstellarsociety.org/BIOENGR2.HTM>

Doing a quick search online, I found that green hydras eat Chlorella algae which could then be eaten by a bigger creature. Additional searches on this same site point out other creatures in the crcle of life for both Chlorella as well as goldfish (a type of carp). And, yes, goldfish will eat Chlorella algae as will crayfish, tilapia, and other tasty morsels.
<http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/green_hydra.htm>

The selection of the aquatic passenger shoud be based on 4 factors:
1) Appetite for algae
2) Edibility by the crew: minimum size?
3) Prolific Reproduction
4) Adaptability to variable living conditions: water pH, food supply, light, heat, etc.

Goldfish definitely score on points 1 & 4, but to be edible, they've gotta be kinda big. Additionally, goldfish don't reproduce well in captivity. Crayfish don't get very big and may be a better choice since they get edible faster at a smaller size. They're not shy reproducers and, with no predators around, are quite prolific. Freshwater shrimp might also be another good possibility.

A related report from "Atomic Rocket" seems to attempt to handle the matter with much scientific deliberation.
<http://www.projectrho.com/rocket/rocket3g.html>

BTW, The first test of animal apssenger survivability isn't 4 months later between Earth and Mars but the short jump from Earth to space. Similarly, the challenge isn't getting this to work as part of a colony on a gravitational sphere, but keeping everything alive in the 0g void between them.

Are you flying goldfish for the heck of it, or do you have a specific experiment in mind? If you're doing it for the heck of it, get a (really) big plastic bag, add some water, drop in some time-dispensing food, add a hardy fish, and it'll survive a month or so. The ammonium takes time to accumulate and as long as you have enough water, it won't be concentrated enough to kill the fish. Then you can find another way to torture it.

If you have a specific experiment in mind, then you should probably pick a different organism. Unless there's someone there tending to it, fish get sick from all kinds of things.

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

I think a better option for breathable air in space would be through a small greenhouse setup. For example, the Sept 1988 experiment by Space Biosphere Ventures was a HUGE success because it was small and limited in both size and scope. Imagine a setup similar to that where the air from the rest of the ship was sucked in and fresh air from the greenhouse was expelled. It'll keep the ship from getting so rank as well as ensure some edible produce for the health of the personnel during the journey. This also makes air "filtration" easier since we don't need to figure out how to get the stale air into the water for the chlorella to act on it.

Plants aren't as gravity dependant and wouldn't face the same risks as the fish. With the plant's root system self-contained, the water could contain chlorella, minerals or whatever else the plants need and can use.

Additionally, with much less energy being expended by the crew on the voyage, the high energy concentrations from meat would be more or less wasted. Therefore, a more vegetarian diet would be better for all concerned. Meat could be added to the diet in other ways and in smaller quantities.

Sizing of the greenhouse'd still be based on the number of people aboard like before. It doesn't need to be an exact figure since you can't really produce "too much" fresh air, but a minimum size should be recognised.

It's also interesting to note that references that are often made to the "living soil". Even in a hydroponic setup, we'd need a measure of dirt to allow the air to interact with it.

Are you flying goldfish for the heck of it, or do you have a specific experiment in mind?

The specific experiment would be to demonstrate life support in a “zero G” system with the lowest practical orbital weight. I expect that an opportunity can be found to fly a satellite weighing a few pounds if that satellite can be expected to demonstrate long duration life support with a closed or nearly closed loop system. Even your “Goldfish in a bag”, will require Oxygen (and CO2 disposal) which can occur on Earth through the bag walls. In space, these gasses must be handled by the life support system. If the nitrogen wastes for the goldfish appear as ammonia, then that must be dealt with as well. I suggest that diffusion through a plastic membrane into a concentrated acidic solution could trap the ammonia in that solution (perhaps as ammonium acetate). Better yet would be trapping in ion exchange beads (retaining the gas transfer membrane to prevent acidification of the fish water itself).

Having personally kept goldfish alive for several years, it seems that demonstrating a “Mars Mission” life support duration (2.7 years) would be a desirable goal. A biological closed loop system is an interesting secondary goal, but this will probably be harder to scale up for human use than the semiclosed system. (“Biosphere 2” certainly demonstrated that this problem was harder than expected.) Other animals remain a possibility, but a small fish still seems about the easiest animal subject which is still “interesting” enough for a public demonstration of significant progress with long duration life support systems in space.

“Biosphere 2” certainly demonstrated that this problem was harder than expected.

Before they did Biosphere 2, they tried something much smaller which was an unqualified success. A localize variety of plants & soil, The problems with Biosphere 2 was they were trying for too much variety as an Earth replacement in too small a space. I agree that such an approach isn't practical (initially) nor is it even what we're trying to achieve.

What would be practical would be more along the lines of a greenhouse in a closet. An enclosed room (~10'x10') filled with hydroponic trays, lights, self-contained water/feed cycling equipment, etc. The air from the rest of the ship could be brought in and exchanged. Keeping it all enclosed allows for micro-environment experiments and tests. The air flow rate through the room could be adjusted experimentally or as needed. Depending on how it was constructed, we could even test effects on the plants of modified air pressure, higher CO2 levels, etc.

The BIGGEST advantage is that the air exchange is all air with no need for all the membranes, acids, etc. that you were talking about needing. You were already considering using the Chlorella plant as a biological CO2 scrubber. The greenhouse becomes part of the life support system both on a daily basis as well as emergency back-up since plants don't necessarily need electricity to transpire as well as a semi-permanent food source.

Further, the air quality in that room should be MUCH better than the rest of the ship. As such, you could go in for a "breath of fresh air" when the rest of the ship's air and overt technology becomes "intolerable" from a psychological standpoint. If kept open to the ship, the purification and air enhancement would be unnoticable, insufficient, and unalterable.